[0001] The present disclosure describes tunable lens and a method for operating a tunable
lens.
[0002] The tunable lens is a refractive optical element, which is arranged to interact with
electromagnetic radiation, in particular visible light, in a definable manner. For
example, the tunable lens is arranged to tune optical properties like optical power
and/or cylinder.
[0003] The tunable lens comprises a fluidic volume, a flexible membrane and a shaping element.
The fluidic volume may be a delimited region, which is at least partially passed through
by electromagnetic radiation during normal operation. In particular, the fluidic volume
is at least partially delimited by the flexible membrane. The fluidic volume is filled
with a fluid which may be in gaseous phase or in liquid phase. In particular the fluidic
volume may be filled with a water-based liquid or with an oil-based liquid.
[0004] The flexible membrane delimits the fluidic volume on one side. In particular, the
fluid is directly adjacent to the flexible membrane. The flexible membrane comprises
an optical surface of the tunable lens. At least on optical property is adjustable
by changing the shape of the flexible membrane. Here and in the following, the term
"flexible" in the context of the membrane describes a property of the membrane which
allows the membrane to be bent obliquely to its main plane of extension. In particular,
the membrane is expandable. Here and in the following the term "expandable" in the
context of the membrane describes a property of the membrane which enables to expand
the membrane reversibly along its main plain of extension.
[0005] The shaping element is attached to the membrane. The shaping element may have a ring
shape. In particular, the shaping element is attached to one surface of the membrane.
In particular, the membrane and the shaping element are connected by a material bonded
connection. Alternatively, the shaping element and the membrane may be fabricated
in a one-piece manner, wherein the shaping element and the membrane are fabricated
simultaneously in common fabrication steps. In particular, the shaping element and
the membrane may comprise a same material. The main planes of extension of the shaping
element and the membrane extend essentially parallel to each other. In a direction
perpendicular to the main plane of extension, the thickness of the shaping element
is larger than the thickness of the membrane. In particular, the stiffness of the
shaping element is larger than the stiffness of the membrane. For example, the shaping
element is arranged to transfer forces along the perimeter of the membrane, to control
the deflection of the membrane along the perimeter of shaping element in a direction
along the optical axis.
[0006] The shaping element surrounds an optically active region of the membrane. During
intended operation, electromagnetic radiation passes through the optically active
region, preferably through the entire optically active region. Here and in the following,
the optically active region is a part of the membrane which is dedicated to form an
optical surface of the tunable lens. In particular, the deformation of the optically
active area is controlled during intended operation in order to adjust the optical
properties of the tunable lens. In particular, the shaping element extends continuously
perimetrically around the optically active region. The shaping element and the membrane
form a common contact surface, which surrounds the optically active region continuously.
In particular, the optically active region is directly adjacent to the shaping element.
As seen in a top view along the optical axis, the shape of the optically active region
is defined by a contour of the shaping element, wherein the contour of the shaping
element is defined by the inner edge of the shaping element, which is adjacent to
the optically active region.
[0007] The shaping element is arranged to alter optical properties of the tunable lens by
deflection. The deflection describes a displacement of the shaping element in a direction
along the optical axis of the tunable lens. In particular a deflection of the shaping
element results in a change of the shape of the membrane, whereby optical properties
of the liquid lens are altered. Additionally, or alternatively, the shaping element
is arranged to limit the deflection of the membrane, to alter optical properties of
the liquid lens in a desired manner.
[0008] In top view, the shaping element has a non-circular contour, wherein the contour
of the shaping element extends within an imaginary circumcircle. In particular, the
optically active region has a non-circular shape as seen in a top view. Preferably
the non-circular shape of the optically active region is identical to the shape of
the contour of the shaping element. Here and in the following, the "top view" is the
perspective perpendicular with respect to the main extension plane of the shaping
element in a non-deflected state. For example, the main plain of extension of the
shaping element extends perpendicularly with respect to the optical axis. The shaping
element may have a non-circular ring-shape seen in a top view. The width of the shaping
element seen in a top view may be constant. Alternatively, the width of the shaping
element may vary at different positions along the ring. The width of the shaping element
is measured along the direction of the radius of the circumcircle. In particular,
the contour of the ring is defined by the inner edge of the shaping element, wherein
the inner edge faces the optically active area of the membrane. Here and in the following,
the circumcircle is an imaginary circle which completely surrounds the contour of
the shaping element, while having a minimum radius. In particular, the circumcircle
may intersect the shaping element, because the inner edge of the circumcircle defines
the contour.
[0009] When tuning the lens, the amount of deflection of the shaping element is proportional
to a lateral distance of the contour to the circumcircle. The lateral distance is
measured along the main plain of extension of the shaping element. Here and in the
following, the lateral distance is measured in the direction of the radius of the
circumcircle. In particular, when altering the optical properties of the tunable lens,
the deflection of a section of the shaping element increases with increasing lateral
distance.
[0010] According to one embodiment, the tunable lens comprises the fluidic volume, the flexible
membrane, and the shaping element. The membrane delimits the fluidic volume on one
side, the shaping element is attached to the membrane and the shaping element surrounds
an optically active region of the membrane. The shaping element is arranged to alter
optical properties of the tunable lens by deflection, in particular in a direction
along the optical axis of the tunable lens. In top view the shaping element has a
non-circular contour, wherein the contour of the shaping element extends within an
imaginary circumcircle, and the amount of deflection of the shaping element is proportional
to a lateral distance of the shaping element to the circumcircle. In particular, the
shaping element is arranged such that essentially all points of the shaping element
lie on the surface of an imaginary spherical surface. In particular, the radius of
curvature of said spherical surface changes when altering the optical properties.
[0011] A tunable lens described here is based on the following considerations, among others.
Tunable lenses having a non-circular contour require a sophisticated control of their
tuning states, to achieve good optical quality. Among other things, the tunable lens
described here makes use of the idea to design the tunable lens such that deflection
of the shaping element depends on the lateral distance between the contour and the
imaginary circumcircle. Advantageously, said feature enables a particularly simple
control of the shape of the optically active region of the membrane by means of the
shaping element.
[0012] According to one embodiment, the shaping element is arranged such that a contour
of the shaping element lies on the surface of an imaginary spherical surface, wherein
a radius of curvature of the imaginary spherical surface changes when altering the
optical properties of the tunable lens. In particular, the optically active area of
the membrane extends along the same imaginary spherical surface.
[0013] According to one embodiment, the tunable lens comprises an actuator, wherein the
actuator is arranged to apply a deflection force to the shaping element. The deflection
force is applied to multiple deflection points of the shaping element, wherein the
absolute value of the deflection force applied at each deflection point is proportional
to a lateral distance of the deflection point to the circumcircle. In particular,
the deflection force is applied non-uniformly at multiple discrete deflection points.
A retention force may act against the deflection force, wherein the retention force
may be derived from the elasticity of the shaping element and/or the membrane. In
particular, the retention force may vary along the perimeter of the shaping element.
[0014] For example, the actuator comprises an electromagnetic unit, a thermomechanical unit,
a piezoelectric unit, a magnetostrictive unit, an electrohydrodynamic unit, an electrostatic
unit, a phase-change unit, a shape memory unit, an electrorhelological unit, diamagnetic
unit, a magnetic unit and/or a manual unit which is arranged to generate at least
a part of the deflection force. The deflection force may be generated by separate
units for each deflection point. Alternatively, one of the units may generate the
deflection force, which is applied to multiple deflection points. The portion of the
deflection force applied to each of the deflection points may depend on the lateral
distance of the deflection point to the circumcircle. The deflection points may be
distributed along the shaping element. In particular, the deflection points are separated
from each other. For example, the deflection force applied to each of the deflection
points is individually controllable.
[0015] According to one embodiment, the tunable lens comprises a mount, wherein the mount
is arranged to apply a retention force to the shaping element. The retention force
is applied to multiple retention points of the shaping element, wherein the absolute
value of the retention force applied at each retention point is proportional to a
lateral distance of the retention point to the circumcircle, and the retention force
acts in an opposite direction of the deflection force. In particular, the retention
force force is applied non-uniformly at multiple discrete retention points. For example,
the mount is a ringshaped element. In a top view, the mount may have essentially the
same shape at the shaping element. In particular, the inner edge of the mount may
have the same shape as the contour of the shaping element.
[0016] The mount may be essentially rigid. In particular, the mount is arranged to not be
deflected due to deflection of the shaping element. At the retention points, the mount
is mechanically coupled to the shaping element. The mount may be coupled by directly
attaching the shaping element at the retention point to the mount. In particular,
the mount is directly attached to the shaping element at retention points which essentially
lie on the imaginary circumcircle. Alternatively, the mount may be coupled to retention
points of the shaping element by means of an elastic element.
[0017] According to one embodiment the deflection force applied to one of the deflection
points is larger for larger lateral distances of the deflection point to the circumcircle
and/or the retention force applied to one of the deflection points is smaller for
larger lateral distances of the retention point to the circumcircle.
[0018] According to one embodiment the deflection points are arranged at distal regions
of the shaping element, wherein at distal regions the shaping element has a local
maximum lateral distance to the circumcircle, and/or the retention points are arranged
at proximal regions of the shaping element, wherein at proximal regions the shaping
element has a local minimum lateral distance to the circumcircle. In particular, the
shaping element comprises sections without retention points and without deflection
points, wherein the deflection of the shaping element in said sections adapts to the
deflection at adjacent deflection points and/or retention points.
[0019] According to one embodiment, the retention points and the deflection points are arranged
alternatingly along the perimeter of the shaping element. For example, multiple deflection
points, in particular all deflections points, have a same lateral distance to the
imaginary circumcircle. Multiple retention points, in particular all retention points
may have a same lateral distance to the imaginary circumcircle. Advantageously, said
arrangement of deflection points and retention points simplifies the deflection of
the shaping element at the deflection points and retention points.
[0020] According to one embodiment, the actuator comprises a lever. Multiple deflection
points or retention points are coupled to the lever at different coupling positions
along the lever, wherein the deflection of the shaping element depends on the respective
coupling position assigned to the deflection point or the retention point. Seen in
a top view, the lever extends along an outer edge of the shaping element, wherein
the outer edge faces away from the optically active surface.
[0021] In particular, the lever is attached to a pivot point, wherein the lever is arranged
to rotate around the pivot point. At the coupling position, the lever transfers a
tensile force to the respective deflection point. In particular, the lever is arranged
to exclusively transfer tensile forces through the coupling points. In particular,
the tunable lens comprises multiple levers, wherein seen in a top view the levers
as a whole extend completely around the shaping element. Coupling elements connect
each coupling point with at least one deflection point or retention point. In particular,
the coupling elements are arranged to allow in-plane rotational movement of the shaping
element with respect to the mount. Here and in the following, an in-plane rotational
movement describes a rotation of the shaping element in its main extension plane,
wherein the center of rotation is within the contour of the shaping element.
[0022] According to one embodiment at least one of the deflection points is coupled to the
actuator by means of an elastic element, and/or at least one of the retention points
is coupled to the mount by means of an elastic element. The absolute value of the
retention force and/or absolute value of the deflection force applied to said at least
one deflection point or applied to said at least one retention point is proportional
to the stiffness of the respective elastic element. In particular, the actuator is
arranged to provide a single stroke, wherein the single stroke is transferred to multiple
deflection points, wherein the deflection of the deflection points depends on the
stiffness of the elastic element coupled to the actor and/or the actuator deflects
the lever, wherein the deflection of the deflection points depends on the respective
coupling point assigned to the deflection points. In particular the coupling element
may be one of the elastic elements, whereby the deflection of the deflection points
depends on both, the coupling position assigned to the respective deflection point
and the stiffness of the elastic element.
[0023] According to one embodiment, the actuator is arranged to apply a deflection force
to the shaping element, wherein the deflection force is applied uniformly to the shaping
element, a retention force acts against the deflection force, wherein the absolute
value of the retention force is proportional to the lateral distance of the contour
to the circumcircle. In this context, a force which is applied uniformly describes
a force which is constant along the perimeter of the shaping element. For example,
the actuator is a hydraulic or pneumatic actuator, wherein the actuator is arranged
to apply a pressure to the shaping element. The retention force may be defined by
means of the stiffness of the shaping element. Alternatively, or additionally the
retention force may be based on the stiffness of the shaping element. In particular
the stiffness of the shaping element may vary along the perimeter of the shaping element.
The retention force may be applied at distinct retention points by means of a mechanical
connection to the mount. In particular, the retention force depends on the stiffness
of the elastic element the respective retention point to the shaping element.
[0024] According to one embodiment, at least one of the deflection force or the retention
force is applied non-uniformly. For example, the deflection force is be applied uniformly
and the retention force is applied non-uniformly, or the retention force is applied
uniformly, and the deflection force is applied non-uniformly, or both the deflection
force and the retention force are applied non-uniformly. Here and in the following,
a force which acts uniformly is a force which is constant along the perimeter of the
shaping element. Here and in the following, a force which acts non-uniformly is a
force which varies along the perimeter of the shaping element. In particular, a force
which is applied non-uniformly is applied at discrete points along the perimeter of
the shaping element.
[0025] According to one embodiment the fluidic volume comprises a lens chamber and a reservoir,
wherein the lens chamber and the reservoir are filled with a fluid. The membrane delimits
the lens chamber, and the actuator is arranged to generate the deflection force by
moving fluid between the lens chamber and the reservoir. In particular, the actuator
is a pumping means, which is arranged to pump fluid between the lens chamber and the
reservoir. In particular, pumping the liquid causes the deflection of the shaping
element and not vice versa.
[0026] According to one embodiment, the actuator is arranged to apply the deflection force
to the shaping element on a side opposed to the membrane. In particular, the actuator
comprises a fluidic chamber, wherein the fluidic chamber is adjacent to the shaping
element. By increasing the pressure in the fluidic chamber, the deflection force is
applied uniformly to the shaping element.
[0027] A method for operating a tunable lens is further disclosed. In particular, the method
can be used to operate a tunable lens described herein. That is, all features disclosed
for the tunable lens are also disclosed for the method and vice versa.
[0028] According to one embodiment, the tunable lens comprises a flexible membrane and a
shaping element, wherein the membrane forms an optical surface of the tunable lens
and the shaping element is attached to the membrane. The shaping element has a non-circular
ring contour in top view and the shaping element surrounds an optically active region
of the membrane. The deformation of the membrane when tuning the lens is controlled
by the deflection of the shaping element in a direction along the optical axis, wherein
the contour of the shaping element extends within an imaginary circumcircle, and the
amount of deflection of the shaping element is proportional to a lateral distance
of the contour to the circumcircle.
[0029] For tuning the tunable lens, the curvature of the membrane in the optically active
region is altered. The curvature of the membrane in optically active region is altered
by controlling the position of the lens shaping element along the optical axis. In
particular, the lens shaping element is flexible, so that the deflection of the lens
shaping element may vary along the perimeter of the lens shaping element in a non-linear
fashion. For example, the deflection of the shaping element is controlled such that
the position of the shaping element along the optical axis has at least one maximum
and/or at least one minimum.
[0030] According to one embodiment, the deflection of the shaping element is controlled
such that the contour of the shaping element lies on an imaginary surface of a spherical
segment, wherein the radius of curvature of said surface of the spherical section
alters, when the tunable lens is tuned. In particular, the dependency of the deflection
h along the optical axis on the lateral distance d between the contour and the circumcircle
is described as follows:

wherein r is the radius of curvature of the optically active region and a is the
radius of the circumcircle. For different tuning states, the radius of curvature r
is changed. The radius of the circumcircle a is given by the shape of the contour.
The lateral distance d between the contour and the circumcircle changes along the
perimeter of the contour and is given by the shape of the contour.
[0031] According to one embodiment, a deflection force is applied to the shaping element
and a retention force is applied to the shaping element, wherein the retention force
and the deflection force act in opposite directions along the optical axis. The deflection
force is applied uniformly to the shaping element and the absolute value of the retention
force is proportional to a lateral distance of the contour to the circumcircle. Here
and in the following, applying the retention force uniformly describes a method in
which the retention force is applied homogeneously to the shaping element. In other
words, the pressure (force per area) is essentially homogeneous along the perimeter
of the shaping element. However, there may be a gradient of the pressure in a direction
perpendicular with respect to the perimeter of the shaping element. In particular,
the retention force is defined by the stiffness of the shaping element, wherein the
stiffness varies along the perimeter of the shaping element. In particular, the retention
force is applied to discrete retention points, wherein the retention force applied
to each retention point controlled to achieve the desired deflection of the shaping
element According to one embodiment, a deflection force is applied to the shaping
element and a retention force is applied to the shaping element, wherein the retention
force and the deflection force act in opposite directions along the optical axis.
The deflection force is applied to discrete deflection points on the shaping element
and the absolute value of the deflection force at each deflection point is proportional
to a lateral distance of the deflection point to the circumcircle and/or the absolute
value of the retention force is proportional to a lateral distance of the shaping
element to the circumcircle. For example, the retention force is applied to discrete
retention points, wherein the retention points are distributed along the perimeter
of the shaping element.
[0032] According to one embodiment the tunable lens comprises a fluidic volume, a flexible
membrane and a shaping element, wherein the membrane delimits the fluidic volume on
one side and the shaping element is attached to the membrane. The shaping element
surrounds an optically active region of the membrane, wherein the shaping element
is arranged to alter optical properties of the tunable lens by deflection, and in
top view the shaping element has a non-circular contour.
[0033] According to one embodiment the optical properties are sphere, cylinder power and
cylinder axis.
[0034] Here and in the following, meridians of the tunable lens describe imaginary straight
lines extending through the center of the circumcircle, wherein different meridians
extend at an angle with respect to each other.
[0035] Sphere (abbreviated as SPH) indicates the amount of lens power, measured in diopters
of focal length. The deflection of the membrane for sphere is equal in all meridians
of the tunable lens. The tunable lens is arranged to alter the lens power by a definable
deformation of the membrane.
[0036] Cylinder (abbreviated as CYL) power indicates the lens power for astigmatism of the
tunable lens. The membrane has a non-spherical surface shape for generating cylinder
power. In particular, for generating cylinder power the membrane has a shape so that
along a first meridian the membrane has no added curvature, and along a second meridian
the membrane has the maximum added curvature, wherein the first meridian and the second
meridian extend perpendicular with respect to each other. The tunable lens is arranged
to alter the curvature of the membrane along the second meridian.
[0037] Cylinder axis describes the angle of the first meridian, which has no added curvature
to correct astigmatism. In other words, the cylinder axis is the angle of the first
lens meridian that is 90 degrees away from the second meridian, wherein the second
meridian contains the cylinder power. The cylinder axis is defined with an angle from
1° to 180°. The tunable lens may be arranged to alter the cylinder axis from 1° to
180°angle.
[0038] In particular, optical properties are prism power and prism axis and add. Prism power
is the amount of prismatic power of the tunable lens, measured in prism diopters ("p.d."
or a superscript triangle). Prism power is indicated in either metric or fractional
English units (0.5 or ½, for example). Prism corresponds to a tilt of the membrane's
surface with respect to the optical axis. Prism power defines absolute of the angle
by which the membrane's surface is tilted. The tunable lens may be arranged to alter
the prism power.
[0039] Prism axis is the direction of prismatic power of the tunable lens. The prism axis
indicates the angle of the meridian around which the surface of the tunable lens is
tilted with respect to the optical axis. The prism axis may extend along any meridian.
The prism axis may be defined by an angle from 1° to 360°. The tunable lens may be
arranged to alter the prism axis from 1° to 360°.
[0040] Add is the added magnifying power applied to a portion of the tunable lens. In particular,
a tunable lens with Add is a multifocal lens. The added magnifying power may range
from +0.75 to +3.00 diopters.
[0041] According to one embodiment the tunable lens comprises at least five actuation points,
wherein at each actuation point is a deflection point, a retention point or both.
Preferably, the tunable lens comprises at least six actuation points, highly preferred
at least eight actuation points. At the actuation points the deflection force and/or
the retention force is transferred to the shaping element. In particular, at the actuation
point the position of the shaping element along the optical axis is definable by the
deflection force and/or the retention force. For example, the actuation points are
discrete points, wherein the shaping element adapts its position along the optical
axis to the deflection of the neighboring actuation points.
[0042] According to one embodiment the actuation points are distributed along the perimeter
of the shaping element and seen in a top view the curvature of the contour has a local
extremum or is zero at the actuation points. In particular, the curvature is measured
within the main plane of extension of the shaping element. In other words, the varying
curvature of the contour results from the non-circular shape of the shaping element.
For example, at the actuation points the shaping element has a local maximum curvature,
a local minimum curvature or zero curvature.
[0043] According to one embodiment the actuation points are distributed along the perimeter
of the shaping element and seen in a top view the curvature of the contour has a same
value at the actuation points. In particular, the curvature of the contour has a same
absolute value at the actuation points.
[0044] According to one embodiment, the actuation points are distributed along the perimeter
of the shaping element, wherein the actuation points are distributed at distances
of equal arc lengths along the perimeter with respect to each other. The arc length
along the perimeter is a length measured along the contour of the shaping element.
[0045] According to one embodiment, the actuation points are distributed along the perimeter
of the shaping element, wherein the actuation points have an equal angel distance
with respect to each other. The angel is measured with respect to the center of the
circumcircle. The angel distance may b for example 72°, 60° or 45°.
[0046] According to one embodiment, the contour of the shaping element is point-symmetric,
and at least two of the actuation points are arranged on opposite sides of the shaping
element with respect to a point of symmetry of the contour. The point of symmetry
may coincide with the center of the circumcircle.
[0047] According to one embodiment, the actuation points which are arranged on opposite
sides of the shaping element have the same deflection in each tuning state. In particular,
the tunable lens is arranged to alter sphere and/or cylinder power and/or prism axis.
[0048] Further advantages and advantageous embodiments and further embodiments of the tunable
lens result from the following embodiment examples shown in connection with the figures.
[0049] It shows:
Figure 1 an exemplary embodiment of a shaping element of a tunable lens in top view;
Figure 2 an exemplary embodiment of a tunable lens in a view perpendicular to a perimeter
of the shaping element;
Figure 3 exemplary embodiments of tunable lenses in a schematic sectional view;
Figures 4 and 5 exemplary embodiments of tunable lenses in a side view;
Figure 6 an exemplary embodiment of a tunable lens in top view;
Figures 7 and 8 exemplary embodiments of shaping elements of tunable lenses in a schematic
perspective view;
Figure 9 a graph showing deflection of an exemplary embodiment of the shaping element
for different tuning states;
Figure 10 the exemplary embodiment of the shaping element described in figure 9 in
a schematic perspective view;
Figure 11, 12 and 13 an exemplary embodiment of a tunable lens having a carrier and
a mount which are connected to the shaping element in a schematic top view;
Figure 14 and 15 exemplary embodiments of tunable lenses, wherein the deflection force
is applied uniformly on the shaping element
Figure 16, 17, 18, 19 and 20 exemplary embodiments of shaping elements of tunable
lenses.
[0050] Elements which are identical, similar or have the same effect are given the same
reference signs in the figures. The figures and the proportions of the elements shown
in the figures to one another are not to be regarded as to scale. Rather, individual
elements may be shown exaggeratedly large for better representability and/or for better
comprehensibility.
[0051] Figure 1 shows an exemplary embodiment of a shaping element 4 of a tunable lens 1
in top view. Here and in the following the top view is along the optical axis 12 of
the tunable lens 1. The shaping element has a non-circular ring shape, and the inner
edge of the shaping element 4 defines a contour 40. The shaping element 4 is connected
to a membrane 3 and circumvents an optically active area of the membrane 3.
[0052] The shaping element 4 extends within an imaginary circumcircle 10. The circumcircle
10 is a circle surrounding the shaping element 4, in particular the contour 40, within
the main extension plane of the shaping element 4, wherein the circumcircle 10 has
the smallest radius possible. A lateral distance d between the circumcircle 10 and
the contour 40 varies along a perimeter 100 of the shaping element 4. The lateral
distance is measured along the radius o the circumcircle 10. The shaping element 4
has a width w which varies along the perimeter 100 of the shaping element 4. The width
w is measured in a direction along the radius of the circumcircle 10.
[0053] Figure 2 an exemplary embodiment of a tunable lens 1 in a schematic view perpendicular
to the perimeter 100 of the shaping element 4. The shaping element 4 is attached to
a mount 6 and a carrier 50, wherein the mount 6 and the carrier 50 are arranged on
opposite sides of the shaping element long the optical axis 12 of the tunable lens
1. For example, the mount 6 and/or the carrier 50 has the same shape as the shaping
element 4 or is congruent to the shaping element 4. For tuning the tunable lens 1,
the carrier 50 is moved along the optical axis 12 by means of an actuator 5. The carrier
50 applies a displacement force 51 to the shaping element 4. The mount 6 essentially
maintains its position along the optical axis 12 when the tunable lens 1 is actuated.
The mount 6 is arranged to apply a retention force 61 to the shaping element 4. The
retention force 61 acts in an opposite direction as the deflection force 51.
[0054] The shaping element 4 comprises deflections points 41 and retention points 42. At
the deflection points 41 at least a portion of the deflection force 51 acts on the
shaping element. At the retention points at least a portion of the retention force
61 acts on the shaping element 4. At the displacement points 41 and the retention
points 42, the shaping element 4 may be directly attached to the carrier 50 and the
mount 6 or the shaping element 4 may be attached to the mount 6 and the carrier 50
by means of elastic elements 53. In particular, the retention points 42 and the deflection
points 41 are spaced apart from one another. For example, the retention points 42
and the deflection points 41 are arranged alternatingly along the perimeter 100 of
the shaping element 4. The retention force 61 and the deflection force 51 are applied
such that the deflection of the shaping element 4 along the optical axis 12 is proportional
to the lateral distance d between the shaping element 4 and the circumcircle 10. In
particular, for larger lateral distances d, the deflection of the shaping element
4 increases.
[0055] Figure 3 shows an exemplary embodiment of tunable lens 1 in a schematic sectional
view. The Tunable lens 1 comprising a fluidic volume 2, the flexible membrane 3 and
the shaping element 4. The membrane 3 delimits the fluidic volume 2 on one side along
the optical axis 12. The shaping element 4 is attached to the membrane 3 and the shaping
element 4 surrounds an optically active region of the membrane 3. The shaping element
4 is arranged to alter optical properties of the tunable lens 1 by deflection along
the optical axis 12. In top view the shaping element 4 has a non-circular contour
40, wherein the contour 40 extends within an imaginary circumcircle 10, and the amount
of deflection of the shaping element 4 is proportional to a lateral distance d of
the contour 40 to the circumcircle 10.
[0056] For controlling the tunable lens 1, the deflection force 51 is applied to the shaping
element 4 and the retention force 61 is applied to the shaping element 4, wherein
the retention force 61 and the deflection force 51 act in opposite directions along
the optical axis 12. The deflection force 51 is applied uniformly to the shaping element
4 and the absolute value of the retention force 61 is proportional to a lateral distance
d of the contour 40 to the circumcircle 10.
[0057] The tunable lens 1 comprises an actuator 5, wherein the actuator 5 is arranged to
apply the deflection force 51 to the shaping element 4. The deflection force 51 is
applied uniformly to the shaping element 4. The deflection force 51 acts in an opposite
direction of the retention force 61, and the absolute value of the retention force
61 is proportional to the lateral distance d of the contour 40 to the circumcircle
10.
[0058] Tunable lens 1 comprises the mount 6, which is arranged to apply the retention force
61 to the shaping element 4. In a top view, the mount 6 may have a ring shape, in
particular a non-circular ring shape. The retention force 61 is applied to multiple
retention points 42 of the shaping element 4, wherein the absolute value of the retention
force 61 applied at each retention point 42 is proportional to a lateral distance
d of the retention point 42 to the circumcircle 10. The retention points 42 may be
connected to the mount 6 by means of an elastic element 53, which transfers the retention
force 61 to the shaping element 4. In particular, the portion of the retention force
61 which is transferred via the elastic element 53 depends on the stiffness of the
elastic element 53. The retention points 42 may be directly attached to the mount
6.
[0059] The retention force 61 may at least partially result from the elastic modulus of
the shaping element. The elastic modulus of the shaping element 4 may vary along the
perimeter of the shaping element 4. For example, the shaping element 4 has a thickness
t, wherein the thickness t is measured along the optical axis 12. The thickness t
varies along the perimeter 100 of the shaping element 4, which results in a variation
of the elastic modulus of the shaping element 4 along the perimeter 100. In particular
the elastic modulus of the shaping element 4 is proportional to the lateral distance
d of the shaping element 4. In particular, with increasing lateral distance d the
elastic modulus of the shaping element decreases along the perimeter 100. Thus, the
thickness t of the shaping element 4 may be proportional to the lateral distance d.
In particular, the thickness t increases with decreasing lateral distance d along
the perimeter 100.
[0060] The fluidic volume 2 comprises a lens chamber 21 and a reservoir 22, wherein the
lens chamber 21 and the reservoir 22 are filled with a fluid. In particular the lens
chamber 21 and the reservoir 22 are filled with the same fluid. The fluid may be water-based-
oil-based or may be in a gaseous phase. In particular, the refractive index of the
fluid differs from the refractive index of a material, which is arranged on an opposite
side of the membrane 3. The membrane 3 delimits the lens chamber 21, and the actuator
5 is arranged to generate the deflection force 51 by moving fluid between the lens
chamber 21 and the reservoir 22. In particular, the actuator comprises a pumping unit,
which alters the pressure in the lens chamber 21, to change the tuning state of the
tunable lens. The deflection force is applied uniformly to the shaping element 4 by
increasing the pressure in the lens chamber 21. The lens chamber is delimited by the
membrane 3, the mount 6, a window element 7 and a bellows 30. The bellows 30 connects
the mount 6 and the shaping element and/or the membrane 3 in a liquid-tight fashion.
The bellows 30 may be integrally formed with the membrane. In particular, the elastic
element(s) may be integrally formed with the bellows 30. The bellows may be a folded
membrane, which enables a displacement of the shaping element 4 along the optical
axis 12 with respect to the mount 6.
[0061] Figure 4 shows an exemplary embodiment of a tunable lens 1 in a schematic side view.
The actuator 5 comprises a lever 52, and multiple deflection points 41 are coupled
to the lever 52 at different coupling positions 520 along the lever 52. The deflection
of the shaping element 4 depends on the respective coupling position 520. The lever
52 is rotatably attached to the mount 6 by means of a pivot point 522. Coupling elements
521 transfer the deflection force 51 between the coupling points and the deflection
points 41. In particular, the coupling elements 521 allow relative movement of the
deflection points 41 with respect to the couplings points 520 in directions perpendicular
to the optical axis 12. In particular, the coupling elements 521 are arranged to solely
transfer tensional forces between the lever 52 and the shaping element 4.
[0062] In particular, the coupling element 521 may be an elastic element 53 having a dedicated
elastic modulus. At least one of the retention points 42 is coupled to the mount 6
by means of an elastic element 53, wherein absolute value of the deflection force
51 applied to said at least one deflection point 41 is proportional to the stiffness
of the respective elastic element 53.
[0063] Figure 5 shows an exemplary embodiment of the tunable lens 1 in a schematic side
view. The tunable lens 1 comprises levers 52, which are respectively attached to the
mount 6 by means of the pivot point 522. The levers 52 are coupled to the window element
and to the shaping element 4 by means of coupling elements 521. The actuator 5 is
arranged to apply a force to the window element 7, whereby the window element 7 is
displaced with respect to the mount 6. The window element 7 and the mount 6 are connected
by means of a bellows 30 in a liquid-tight manner. The movement of the window element
7 causes a rotation of the levers 52 around the pivot points 522. The rotation of
the levers 52 results in a displacement force 51 acting on displacements points 41
of the shaping element 4. The position of the coupling points 520 assigned to each
deflection point 41, defines the stroke of each displacement point 41 along the optical
axis.
[0064] Figure 6 shows an exemplary embodiment of a tunable lens 1 in a schematic top view
along the optical axis 12. The shaping element 4 has a uniform width w. The levers
52 respectively extend along an outer edge of the shaping element 4, wherein the outer
edge is opposed to the contour 40. Each lever 52 is coupled to the actuator 5, to
the mount 6 by means of a pivot point 522 and to the shaping element by means of the
coupling elements 521.
[0065] Figure 7 shows an exemplary embodiment of a shaping element 4 of a tunable lens 1
in a schematic perspective view in one specific tuning state. The shaping element
4 has a non-circular contour. The deflection of the shaping element 4 is controlled
such that the contour 40 of the shaping element 4 lies on a surface 11 of an imaginary
spherical segment. When tuning the tunable lens 1, the radius of curvature of the
imaginary spherical segment changes. In particular, the radius of curvature of the
imaginary spherical segment decreases, when the optical power of the tunable lens
increases.
[0066] Figure 8 shows an exemplary embodiment of a shaping element 4 of a tunable lens 1
in a schematic perspective view in one specific tuning state. The shaping element
surrounds an optically active region of the membrane 3. The shaping element 4 is controlled
such that the contour of the shaping element 4 lies on the surface 11 of the imaginary
spherical segment. In particular, the optically active region of the membrane extends
along the surface 11 of the imaginary spherical segment.
[0067] Figure 9 depicts a graph showing deflection of an exemplary embodiment of the shaping
element 4 for different tuning states. The deflection of the shaping element 4 along
the optical axis 12 is plotted against the perimeter 100 of the shaping element 4.
Each curve represents the deflection of the shaping element 4 in one tuning state.
From top to bottom, the optical power of the tunable lens 1 increases, wherein the
deflection of the shaping element 4 along the optical axis 12 increases. In the graph,
a single deflection point 41 or a single retention 42 point is enclosed by a dashed
line. When tuning the tunable lens 1 towards higher optical power, the distance of
deflection points and retention points along the optical axis increases. The deflection
points 41 may be commonly connected to the carrier 50, whereby the deflection points
have a same position along the optical axis 12 for each tuning state. The retention
points 42 may be commonly connected to the mount 6, whereby the retention points 42
have a same position along the optical axis 12 for each tuning state. For example,
in between the retention points and the deflection points, the position of the shaping
element 4 along the optical axis 12 is not defined.
[0068] Figure 10 shows the exemplary embodiment of the shaping element 4 described in figure
9 in one tuning state in a schematic perspective view. The deflection points 41 and
the retention points 42 are arranged along the perimeter 100 spaced apart from one
another. Alternatively, at least some of the retention points 42 and some of the deflection
points 41 may coincide. Furthermore, the deflection force 51 and or the retention
force may be applied extensively to the shaping element 4.
[0069] Figures 11, 12 and 13 show an exemplary embodiment of a tunable lens 1 having a carrier
50 and a mount 6 which are connected to the shaping element 4 in a schematic top view.
[0070] Figure 11 shows solely the carrier 50, which is connected to the deflection points
41 by means of links 52 and by means of an elastic element 53. The elastic element
is a bending beam structure. The stiffness of the elastic element 53 depends on the
geometry of the bending beam structure. The links 54 provide a stiff connection between
the carrier 50 and the shaping element 4. Thus, the deflection of the carrier 50 corresponds
the deflection of the shaping element 4 at the deflection point 41 which is connected
by means of the link 54. In particular, the carrier 50 is connected to the shaping
element 4 by means of links 54 at deflection points 41, wherein the lateral distance
d between the contour 40 and the circumcircle 10 has a local maximum.
[0071] Figure 12 shows solely the mount 6, which is connected to the retention points 42
by means of links 52 and by means of the elastic elements 53. The elastic elements
53 are bending beam structures. The stiffness of the elastic elements 53 depends on
the geometry of the bending beam structures. The links 54 provide a stiff connection
between the mount 6 and the shaping element 4. Thus, the deflection of the mount 6
corresponds the deflection of the shaping element 4 at the retention point 42 which
is connected by means of the link 54. In particular, the mount 6 is not deflected
for tuning the tunable lens 1. Thus, the retention points 42 connected by means of
the link 54 remain at the same position for every tuning state. In particular, the
carrier mount 6 is connected to the shaping element 4 by means of links 54 at retention
points 42, wherein the lateral distance d between the contour 40 and the circumcircle
10 has a local minimum, in particular the lateral distance d is zero.
[0072] Figure 13 shows the tunable lens with both, the carrier 50 and the mount 6 with their
corresponding connections to the shaping element 4 in schematic top view. The embodiment
shown in figure 13 comprises the mount 6 and the carrier 50 shown in figure 11 and
12. The carrier 50 and the mount 6 are congruent.
[0073] Figure 14 and 15 show exemplary embodiments of tunable lenses 1, wherein the deflection
force 51 is applied uniformly on the shaping element 4. The tunable lens comprises
a pressure chamber 55 which is arranged to transfer pressure to the shaping element
4.
[0074] In the exemplary embodiment shown in figure 14, the shaping element 4 is arranged
on a side of the membrane 3 facing away from the fluidic volume 2. The actuator 5
is arranged to alter the pressure in the pressure chamber 55. The shaping element
4 is movably mounted and guided in the pressure chamber. The shaping element 4 delimits
the pressure chamber 55 on one side. The pressure in the pressure chamber 55 is distributed
uniformly on the shaping element 4. The shaping element 4 is displaced along the optical
axis 12 by altering the pressure in the pressure chamber 55.
[0075] The fluidic volume 2 is delimited by the window element 7, the mount 6, the bellows
30 and the membrane 3. In particular the lens volume 2 is enclosed in a liquid-sealed
manner. The bellows may act as elastic element 53, which transfers retention force
61 from the mount 6 to the shaping element 4. Increasing the pressure in the pressure
chamber 55 results in an increased pressure in the liquid chamber 2, which causes
a deflection of the shaping element 4, whereby the curvature of the membrane 3 is
increased.
[0076] Compared to the embodiment shown in figure 14, the embodiment shown in figure 15
the liquid chamber 2 is arranged on the other side of the membrane 3. In figure 15
the liquid chamber 2 is enclosed by the window element 7 the shaping element 4, the
pressure chamber 55 and the membrane 3. Increasing the pressure in the pressure chamber
55 results in a decreased pressure in the liquid chamber 2, which causes a deflection
of the shaping element 4, whereby the curvature of the membrane 3 is reduced. The
mount is coupled to the shaping element 4 by means of an elastic element 53, which
transfers the retention force 61 from the mount 6 to the shaping element.
[0077] Figure 16 shows an exemplary embodiment of the shaping element 4 of a tunable lens
1 in a schematic top view, wherein the tunable lens is arranged to alter are sphere,
cylinder power and cylinder axis in a definable manner. In particular, the tunable
lens 1 comprising the shaping element 4 is arranged to alter prism power, prism axis
and add in a definable manner. The shaping element 4 comprises five actuation points
43, wherein at each actuation point 43 is a deflection point 41, a retention point
42 or both. The actuation points 43 are distributed along the perimeter 100 of the
shaping element 4 and seen in a top view the actuation points 43 are located at positions
where curvature of the contour 40 has a local extremum or is zero.
[0078] Figure 17 shows an exemplary embodiment of the shaping element 4 of a tunable lens
1 in a schematic top view. The shaping element 4 comprises five actuation points 43,
which are distributed along the perimeter 100 of the shaping element 4 and seen in
atop view the curvature of the contour 40 at the actuation points 43 has a same value.
In this particular case, the curvature of the contour 40 at the actuation points is
zero.
[0079] Figure 18 shows an exemplary embodiment of the shaping element 4 of a tunable lens
1 in a schematic top view. The shaping element 4 comprises eight actuation points
43, which are distributed along the perimeter 100 of the shaping element 4. The contour
40 of the shaping element 4 is point-symmetric. At least two of the actuation points
43 are arranged on opposite sides of the shaping element 4 with respect to a point
of symmetry 44 of the contour 40. The actuator 5 is arranged such, that the actuation
points 43 which are arranged on opposite sides of the shaping element 4 have the same
deflection along the optical axis in each tuning state of the tunable lens 1.
[0080] Figure 19 shows an exemplary embodiment of the shaping element 4 of a tunable lens
1 in a schematic top view. The shaping element 4 comprises eight actuation points
43, which a distributed along the perimeter 100 of the shaping element 4. The actuation
points 43 have an equal angel distance with respect to each other. The angel distance
is measured with respect to the center of the circumcircle 10 of the shaping element
4. In the present case, the actuation points 43 are arranged at an angle distance
alpha of 45° with respect to each other.
[0081] Figure 20 shows an exemplary embodiment of the shaping element 4 of a tunable lens
1 in a schematic top view. The shaping element 4 comprises six actuation points 43,
which a distributed along the perimeter 100 of the shaping element 4. The actuation
points 43 are distributed at distances of equal arc lengths (45) along the perimeter
100 with respect to each other.
[0082] The invention is not limited to the embodiments by means of which the invention is
described. Rather, the invention encompasses any new feature as well as any combination
of features, which in particular includes any combination of features in the claims,
even if that feature or combination itself is not explicitly stated in the claims
or embodiments.
List of reference signs
[0083]
- 1
- tunable lens
- 2
- fluidic volume
- 3
- membrane
- 4
- shaping element
- 5
- actuator
- 6
- mount
- 7
- window element
- 30
- bellows
- 10
- circumcircle
- 11
- surface of spherical section
- 12
- optical axis
- 21
- lens chamber
- 22
- reservoir
- 40
- contour
- 41
- deflection point
- 42
- retention point
- 43
- actuation point
- 44
- Point of symmetry
- 45
- arc length
- 50
- carrier
- 51
- deflection force
- 52
- lever
- 53
- elastic element
- 54
- link
- 55
- pressure chamber
- 520
- coupling position
- 521
- coupling element
- 522
- pivot point
- 100
- perimeter of shaping element
- d
- lateral distance
- w
- width of shaping element
1. Tunable lens (1) comprising a fluidic volume (2), a flexible membrane (3) and a shaping
element (4), wherein
the membrane (3) delimits the fluidic volume (2) on one side,
the shaping element (4) is attached to the membrane (3),
the shaping element (4) surrounds an optically active region of the membrane,
the shaping element (4) is arranged to alter optical properties of the tunable lens
(1) by deflection,
in top view the shaping element (4) has a non-circular contour (40), wherein the contour
(40) extends within an imaginary circumcircle (10), and
the amount of deflection of the shaping element (4) is proportional to a lateral distance
of the contour (40) to the circumcircle (10).
2. Tunable lens (1) according to claim 1, wherein the shaping element is arranged such
that n contour of the shaping element lies on the surface of an imaginary spherical
surface, wherein a radius of curvature of the imaginary spherical surface changes
when altering the optical properties of the tunable lens.
3. Tunable lens (1) according to claim 1 or 2, comprising an actuator (5), wherein
the actuator (5) is arranged to apply a deflection force (51) to the shaping element,
the deflection force (51) is applied to multiple deflection points (41) of the shaping
element (4), wherein the absolute value of the deflection force (51) applied at each
deflection point (41) is proportional to a lateral distance (d) of the deflection
point (41) to the circumcircle, and/orthe tunable lens comprises a mount (6), wherein
the mount (6) is arranged to apply a retention force (61) to the shaping element (4),
the retention force (61) is applied to multiple retention points (42) of the shaping
element (4), wherein the absolute value of the retention force (61) applied at each
retention point (42) is proportional to a lateral distance (d) of the retention point
(42) to the circumcircle (10).
4. Tunable lens (1) according to claim 4, wherein
the deflection force (51) applied to one of the deflection points (41) is larger for
larger lateral distances (d) of the respective deflection point (41) to the circumcircle
(10), and/or
the retention force (61) applied to one of the retention points (42) is smaller for
larger lateral distances (d) of the retention point (42) to the circumcircle (10).
5. Tunable lens (1) according to claim 3 or 4, wherein
the deflection points (42) are arranged at regions of the shaping element (4), where
the contour (40) has a local maximum lateral distance (d) to the circumcircle (10),
and/or
the retention points (42) are arranged at regions of the shaping element (4), where
the contour (40) has a local minimum lateral distance (d) to the circumcircle (10).
6. Tunable lens (1) according to claim 3 or 4, wherein the retention points (42) and
the deflection points (41) are arranged alternatingly along the perimeter (100) of
the shaping element (4).
7. Tunable lens according to one of the preceding claims, wherein at least one of the
deflection force (51) or the retention force (61) is applied non-uniformly to the
shaping element (4).
8. Method for controlling a tunable lens (1), wherein the tunable lens (1) comprises
a flexible membrane (3) and a shaping element (4), wherein
the membrane (3) forms an optical surface of the tunable lens (1),
the shaping element (4) is attached to the membrane (3),
the shaping element (4) has a non-circular ring contour (40) in top view,
the shaping element (4) surrounds an optically active region of the membrane (3),
wherein the deformation of the membrane (3) when tuning the lens (1) is controlled
by the deflection of the shaping element (4) in a direction along the optical axis
(12), wherein
the contour (40) of the shaping element (4) extends within an imaginary circumcircle
(10), and
the amount of deflection of the shaping element (4) is proportional to a lateral distance
(d) of the contour (40) to the circumcircle (10).
9. Method according to claim 8, wherein
the deflection of the shaping element (4) is controlled such that the contour (40)
of the shaping element (4) lies on a surface (11) of an imaginary spherical segment,
wherein the radius of curvature of said spherical segment alters when the tunable
lens (1) is tuned.
10. Method for controlling a tunable lens (1) according to claim 8 or 9, wherein
a deflection force (51) is applied to the shaping element (4) and a retention force
(61) is applied to the shaping element (4),
wherein the retention force (61) and the deflection force (51) act in opposite directions
along the optical axis (12),
the deflection force (51) is applied uniformly to the shaping element (4) and the
absolute value of the retention force (61) is proportional to a lateral distance (d)
of the contour (40) to the circumcircle (10).
11. Method for controlling a tunable lens (1) according to claim 8, wherein
a deflection force (51) is applied to the shaping element (4) and a retention force
(61) is applied to the shaping element (4), wherein
the retention force (61) and the deflection force (51) act in opposite directions
along the optical axis (12),
the deflection force (51) is applied to discrete deflection points (41) on the shaping
element (4) and the absolute value of the deflection force (51) at each deflection
point (41) is proportional to a lateral distance (d) of the deflection point (41)
to the circumcircle (10), and/or
the absolute value of the retention force (61) is proportional to a lateral distance
(d) of the retention point (42) to the circumcircle (10).
12. Tunable lens (1) comprising a fluidic volume (2), a flexible membrane (3) and a shaping
element (4), wherein
the membrane (3) delimits the fluidic volume (2) on one side,
the shaping element (4) is attached to the membrane (3),
the shaping element (4) surrounds an optically active region of the membrane,
the shaping element (4) is arranged to alter optical properties of the tunable lens
(1) by deflection,
in top view the shaping element (4) has a non-circular contour (40).
13. Tunable lens according to one of the preceding claims, wherein the optical properties
are sphere, cylinder power and cylinder axis.
14. Tunable lens (1) according to one of the preceding claims, wherein the tunable lens
(1) comprises at least five actuation points (43), wherein at each actuation point
(43) is a deflection point (41), a retention point (42) or both.
15. Tunable lens (1) according to claim 14, wherein the actuation points (43) are distributed
along the perimeter (100) of the shaping element (4) and seen in a top view the actuation
points (43) are located at positions where curvature of the contour (40) has a local
extremum or is zero.
16. Tunable lens (1) according to claim 14 or 15, wherein the actuation points (43) are
distributed along the perimeter (100) of the shaping element (4) and seen in a top
view the curvature of the contour (40) at the actuation points (43) has a same value.
17. Tunable lens (1) according to claim 14, wherein the actuation points (43) are distributed
along the perimeter (100) of the shaping element (4), wherein the actuation points
(43) are distributed at distances of equal arc lengths (45) along the perimeter (100)
with respect to each other.
18. Tunable les (1) according to claim 14, wherein the actuation points (43) are distributed
along the perimeter (100) of the shaping element (4), wherein the actuation points
(43) have an equal angel distance with respect to each other.
19. Tunable lens (1) according to 14, wherein the contour (40) of the shaping element
(4) is point-symmetric,
at least two of the actuation points (43) are arranged on opposite sides of the shaping
element (4) with respect to a point of symmetry (44) of the contour (40).
20. Tunable lens according to claim 19, wherein actuation points (43) which are arranged
on opposite sides of the shaping element (4) have the same deflection in each tuning
state.